A metallic coating film sparkles when there occur reflections from light rays incident on a metallic pigment in the coating film. Metallic coating films have an esthetically attractive appearance of their own with wide variations as in color, and are chiefly applied to metal articles such as automobiles, motor cycles and the like.
A 3-coat 1-bake coating method for forming a metallic coating film is known from Japanese Examined Patent Publication No.25076/1992, the method comprising applying an organic solvent-based thermosetting coating composition comprising a neutralized carboxyl-containing resin having an acid value of 5 to 100 mgKOH/g and an amino resin, adjusting the coating layer to a specific viscosity range, applying an aqueous thermosetting metallic coating composition, applying an organic solvent-based thermosetting clear coating composition, and heating the coatings for curing at the same time.
According to the foregoing conventional coating method, the first layer of organic solvent-based thermosetting coating composition is adjusted to a specific viscosity range while the second layer of aqueous thermosetting metallic coating composition is formed on the viscosity-adjusted first layer, whereby advantageously the amount of the organic solvent can be reduced and the unevenness of metallic effect can be prevented without degrading the esthetic property or surface smoothness of coating film which would occur because of surface roughening and sagging at varied humidities.
However, the foregoing conventional method has drawbacks that the obtained metallic coating film appears flat and deficient in depth feeling, and is not always satisfactory in distinctness-of-image gloss, namely insufficient in esthetic property.